1. Field of the Invention
The present invention relates to a method of image scanning used in a scanner, and more particularly, to an image scanning method that improves scan quality.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram of a prior art scanner 10. The scanner 10 comprises a light source 12 for illuminating a document 14 to be scanned, a transparent panel 16 for supporting the document 14, and a scanning module 18 for scanning light from the document 14. When performing a scan, the light source 12 and the scanning module 18 move simultaneously to scan the document 14.
As shown in FIG. 1, the scanning module 18 has a plurality of light sensors 20 for converting light from the light source 12 to digital image signals. Light is directed to the plurality of sensors 20 by three guiding lenses 22A, 22B, 22C and a lens 24.
A common problem is scratches or dust on one, or more, of the guiding lenses 22A, 22B, 22C, which leads to poor scan quality, examples including, but not limited to, shadows or stripes on the output image.
It is therefore a primary objective of the present invention to provide a method of image scanning that increases the probability of a quality scan.
In a preferred embodiment, the present invention provides a method of image scanning used in a scanner. The scanner comprises a light source for illuminating a document to be scanned, and a scanning module for scanning light from the document and generating an image signal of the document. The scanning module comprises a plurality of light sensors for sensing the light from the document, and a guiding lens for delivering light from the document to the light sensors. The guiding lens moves in a direction perpendicular to the normal of the guiding lens, and it may be set on at least a first and a second position. The method starts by using the light source and the scanning module to obtain a first reference image signal by scanning a reference picture at the first position. At the second position, the light source and the scanning module are used to obtain a second reference image signal by scanning a reference picture. According to the first reference image signal and the second reference image signal, the guiding lens is set to either the first position or the second position. Then, the document is scanned.
If the first reference image signal has fewer flawed areas than the second reference image signal, the guiding lens is moved to the first position to scan the document, and if the second reference image signal has fewer flawed areas than the first reference image signal, the guiding lens is moved to the second position to scan the document.
It is an advantage of the present invention that the probability of a quality scan is increased.
These and other objectives and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.